Import Xournal notebook
EXAMPLES:
>>> from quill.importer.xournal import Xournal
>>> x = Xournal(xournal_file)
>>> print x
<quill.importer.xournal.Xournal object at 0x...>
>>> book = x.get_book()
>>> book.title()
'Example_Notebook'
>>> book.get_page(0)
page number 0
Bases: quill.importer.base.ImporterBase